Topic 5 Revision - Year 9

The substance on which the enzymes act is called ...

Answer explanation

The substance on which the enzymes act is called the substrate.

This is the material that the enzymes bind to and catalyze a chemical reaction.

The substances that are made by the end of a reaction are ...

Answer explanation

The substances that are made by the end of a reaction are called products.

Enzymes are made up of ...

Answer explanation

Enzymes are biological molecules that are made up of proteins.

They play a crucial role in catalyzing various biochemical reactions in living organisms.

The gif image showing long chains of polypeptides being folded to form specific protein molecular structure.

Enzymes increase the rate of a chemical reaction by ________ the activation energy need to start the reaction.

Answer explanation

Enzymes increase the rate of a chemical reaction by lowering the activation energy needed to start the reaction (refer to blue graph).

(Recall: Activation energy is the amount of energy needed to start a reaction)

This means that enzymes make it easier for the reaction to occur by reducing the energy barrier that must be overcome.

By doing so, enzymes speed up the reaction without being consumed in the process.

The same enzymes can be used over and over again

(reused) as they remain unchanged at the end of the reactions.

Thus the enzymes are required only in very ____ amount.

Answer explanation

Enzymes can be reused as they remain unchanged at the end of reactions.

Therefore, only a small amount of enzymes is required.

Enzymes are highly specific: lipids can only be broken down by enzyme ____ into glycerol and fatty acids.

• amylase

• protease

• lipase

• maltase

Answer explanation

One of the characteristics of enzymes is being highly specific in their reaction.

For example, substrate lipids can only be broken down by enzyme lipase into glycerol and fatty acids.

Enzymes are highly specific: proteins can only be broken down by enzyme ____ into amino acids.

• amylase

• protease

• lipase

• maltase

Answer explanation

One of the characteristics of enzymes is being highly specific in their reaction.

For example, the substrate proteins can only be broken down by enzyme protease into amino acids.

Enzymes are highly specific: starch can only be broken down by enzyme ____ into maltose.

• amylase

• protease

• lipase

• maltase

Answer explanation

One of the characteristics of enzymes is being highly specific in their reaction.

For example, the substrate starch can only be broken down by the enzyme amylase into maltose.

In a lock-and-key hypothesis, the lock is always the ...

Answer explanation

In a lock-and-key hypothesis:

(i) the lock is always the enzyme.

(ii) the key is always the substrate.

This process is similar to how a key (substrate) fits into a lock (enzyme), hence the name lock-and-key hypothesis.

Enzyme specificity is due to the ______ of the substrates and the enzymes being complementary to each other.

• temperature

• pH

• three dimensional (3-D) shapes

• concentration

Answer explanation

Enzyme specificity is determined by the three-dimensional shapes of the substrates and the enzymes. The enzymes have complementary shapes to the substrates, allowing them to bind and catalyze specific reactions. This is explained in lock-and-key hypothesis.

Factors such as temperature, pH, and enzyme and substrate concentrations can also affect enzyme rate of reaction, but the primary determinant of specificity is the matching of shapes between the substrates and enzymes.